Apparatus for recovering solvents.



Patented. Dec. 26, 1916.

APPLICATION FILED OCT. 7, 1912.

OQO

I. BAKEIL APPARATUS AFOR RECOVERING SOLVENTS.

APPLICATION FILI-:D ocT. 7, I9Iz.

Patenwd Dee. 26,1916.

2 SHEETS-SHEET 2.

SalI/enf J7)//119 rnEoDonE BAKER., ,or WILMINGTON, DELAWARE, nssIGNon To E. r. DU' PONT DE NEMO POWDER. COMPANY, OEWIEMINnT'oN, DELAWARE, .a conPonATroN or NEW JERSEY.

To all whom z't'mag/ concern:` Y

Be it known that l, TriEoDoRE BAKER, of Wilmington, in the county of New Castle,

and inthe'State of Delaware, have invented a certain new and useful Improvement in'v an Apparatus for Recovering Solvents,l and do hereby declare that the following is a full, clear, and exact description thereof.

My invention relates particularlyv to. a means for recovering. solvents used in coat'- ing compositions, althoughvit may be adapted to use in any other connection where it is desired to recover. solvents. p

My invention isparticularly vapplicable to the recoveryA of solvents from coatings'of paper or -teXtile fabrics containing india the'solvent.'y v

' My invention is-carriedgout by passing the goods in a continuous coated web through an evaporating chamber where it submitted tothe .actionof a heated curl",j-'rent of `air. The air in the evaporating 'chamber having taken up :the solvent Y ent temperatures and the ,diiier'ent quant l of. solvent vvapor carried bythe circulatin air. klt is advantageous to provide agcircu .lation which is effectedl without the' o'f Y special "forcing means yfor the reason "that 4great ldifferences irrlocalypressuresare there? -J 'by avoided and there is notthe great consef purification, is ein evaporated, isconducted ,to a condenser,

where a portion of the solvent is condensed,

the air'with' the residual solvent being again heated and returned to` .the evaporating chamber, While the condensed 'solventQafter coating compositions. ,v

vapors in the interior ofthey yapparatus,5to' eec'ththe 'circulation thereof. lThe vapors within 'the interior of the evaporating chainber have di'erent .densitiesowingto di Specification of Letters Patent.

ployed in preparing freshv Aros Eon nEcovEnINe soLvENrs.

in the type of circulation which l use, there 1s no mechanical apparatus to break down and thereby-stop the circulation during the operation' vof the apparatus.

Whlle my fv process is, capable of being carried out 11n many dier'ent types of apparatus, I havey shown only certain modi- ]Pf'atented Dec. 26, 1916. application med october 7, 1912. serial No. 724,309.' v i cations of apparatus which l may use, in

the accompanying drawings, in which- Figure 1 is a vertical transverse section of oneform of apparatus in which my process may be carried out, the parts being shown somewhat diagrammatically; Fig. 2 1s a slmllar view of another type of apparatus which E may use; Fig. 3 is a similar View of still another type of apparatus; Flg.` 4 is' a similar view of another type of apparatus used for the same purpose; Fig. 5 1s also asimilar view of another type of apparatus used for the same purpose, and Fig. 6 is a vertical section of a portion of an apparatus sealed Awith adhesive tape.

,In the drawings, reference being hadto Fig. 1, a traveling web. 1 of' paper or textile fabric, after being coated, is conveyed through an evaporating chamber 2 by any' suitable means. While inthe evaporating chamber 2, the web l passes beneath a series vo'f heating coils 3 for evaporating the vola- A tlleliquids from the-coating composition.I "The evaporatingv chamber is covered by an easily-.removable cover 4, the edges of which are rendered air-tight by being retained in a liquid seal 5,;'iilled with castor oil or other 11quid,'or in ally other convenient mannenas by fastening with adhesive tape. The current of air wh1ch is circulating through said chaml ,berv 1s led therefrbin downwardly through afvertical passag containing, at the upper y n u n "end thereof, a serieso `cooling coils 7 to in' In carrylngout my n uventronl advantage isl taken of the difference in densities of the-v crease the specific gravity of the solvent- 1rl carrying the solvent vapors lis then conucted through a horizontally disposed conseries vof coils 9 is fed with a current of cold At' the bottom of the conladen air, and tocool the same preliminary ",to ..the condensatlon and'separation of the solvent therefrom. The cooled current of 10o" denser 8 over a series of cooling coils 9. The l water or other refrigerating'agent through j'a'n 'inlet 10 and 'discharges thesame through anzroutlet 11.

denser 8 there isa discharge pipe 12'for the Y *condensed solvent. rlhe air having had art j ofiits contained solvent removed by con cnf sation is reheated ,in any convenient manner as by passing over steam coils 14. The density being thereby reduced, it rises through a vertical passageway 13 and then returns to the evaporating chamber for reuse as before. A baiile 15 is provided to keep scrapings of coating material from falling down the flue 13 and to better direct the circulationof the air.

The type of apparatus shown in Fig. 2 is constructed in the same manner as that shown in Fig. 1, except that an elevated side chimney is employed to assist the draft,thus enabling the other parts to be built more compactly without sacrificing the efficiency of circulation, attained in the form shown in Fig. 1. In the form shownin Fig. 2, this difference in construction requires the solvent-laden air to be led downwardly past a baffle plate 16 to an upwardly directed chamber 17 over a baffle plate 18, and downwardly through the vertical passageway 6, over the cooling coils 7. The long passageway 6 materially assists in giving the circulating current of air the required speed. e

The form of apparatus shown in Fig. 3 is the same as that shown in Fig. 1, except as follows: After leaving the evaporating chamber 2, the solvent-laden air is conducted directly into a horizontal flue 19 located ime mediately below the evaporating chamber and from this point it is led directly to the vertically disposed condenser 20 having a set of cooling coils 21. The air which has been freed from the surplus solvent is thereafter led into contact with the reheating coils 14 located in the vertical passageway 13. This arrangement avoids the loss of any space in the middle of the apparatus between the several chambers.

Another and more compact form lof apparatus is shown in Fig. 4 in which the construction is the same asin the case of the modification shown in Fig. 1, except that the condenser 8 is located immediately below the evaporating chamber 2, the vertical passageways 6 and 13 being made much wider to compensate for their shortness, and baille plates 22 and 23 being located at the inlet and outlet ends of the condenser at the top thereof, and a baille plate 24 being located at the bottom ofthe condenser at the outlet thereof to keep the condensed solvent away from the reheating arrangement.

In Fig. 5 I have shown a type of apparatus which is the same 'as that shownin Fig. 4, except-that a passageway 17 and a passageway 6, together with baffle plates 16 and .18 are utilized which' are similar to .those the advantage that the condensed solvent is,

deliveredat a high level, and that the space below the apparatus is entirely unencumbered.

In Fig. 6 I have shown an adhesive tape 24aL for sealing the cover. l

The operation of my process is substantially the same in all of the different forms of apparatus, and is as follows: The coated web' being constantly moved through the apparatus, the body of air contained therein is irst heated by the reheating coils, thereby decreasing its density, and increasing its evaporating capacity. The heated current of air is then conducted over the coated Surface which is at the same time subjected tov the heat radiated from the heating coils located above the same. Theheat lost by the coated web and the air in contact with it, due to the .latent heat of evaporation is made good by radiation from the coil above in the upper part of the evaporating chamber, thus enabling a smaller volume of circulated air to effect the same amount of evaporation and a higher concentration ,of evaporated solvent to be reached, as well as more uniform and rapid drying, without risk of overheating. The current-of air carrying a large percentage of evaporated solvent, is now cooled to the saturation point by contact with the cooling coils 7. The mixed air and solvent vapors thereupon acquire their greatest density, and fall at considerable speed downwardly vthrough the vertical dpassageway 6 until the condenser is reache The available part of the solvent is then condensed upon ,the surface of the cooling coils in the condenser, and is separated out and removed through the discharge pipe 12 located at the bottom thereof. A portionv of the solvent ICC having now been separated from the curl rent of air, the latter is again conducted upwardly into contact with the heating, coils 14, thereby decreasingv the specific gravity of the same and causing it to again circulate in contact with the coating to be dried.

While I have shown and described above only certain forms of the process and apparatus which may be used for the carrying out of my invention, I wish it to be understood that many changes may be made4 therein without departing from the fimdamental principles thereof.

I claim:

1. In a device of the character described, means for heating a traveling web, an evaporating chamber inclosing the web and heater, and means located below the evaporating chamber for circulating a current of a gas through the same by convection, comprising aV passageway of restricted cross-sectional area located below the evaporating chamber and connected by its two ends to the chamberat its opposite sides,

and a condenser located in the-lowest available part of said passageway.

2. In a device of the character described, an evaporating chamber, means for circulating a current of a gas through the same vthe evaporating chamber, and a condenser located in the lowest available part of the passageway.

3. In a device of the character described,

means for heating a traveling web, an evap-y orating chamber inclosing the web .and heater, and means for circulating a current of a gas through the same by convection, comprising a passageway 'of restricted cross-sectional area, located below the evaporating chamber and connected by its two ends to the chamber at its opposite sides, a preliminary cooler located in the passageway at the outlet from and below the evaporating chamber, and a condenser located in the lowest available part of the passageway.

4. In a device of the character described, an evaporating chamber and means for circulating a current of a gas through the same by convection, comprising a passageway ot' restricted cross-sectional area located below the evaporating chamber and connected by its two ends to the chamber at its opposite sides, a preliminary cooler located inthe passageway at the outlet from and below the evaporating chamber, a preliminary'heater located in the passageway in advance of the evaporating chamber, and a condenser located in the lowest available part of the passageway.

5. ln a device of the character described,

means for heating a traveling web, an evaporating chamber inclosing the web and heater, and means for circulating a current of a gas through the same by convection, comprising a passageway of restricted cross-sectional area located below the evaporating chamber and connected by its two endsto the chamber at its opposite sides, a preliminary cooler located in the passageway at the outlet from and below the evaporating chamber, a preliminary heater located in the passageway in advance of the evaporating chamber, and a condenser located in the lowest available part of the passageway.

6. In a device of the character described, means for heating a traveling web, an evaporating chamber inclosing the web and heater, and means for circulating a current of a gas through the same by convection, comprising a passageway of restricted cross-sectional area passing below the evaporating chamber and connected by its two ends to the chamber at its opposite sides, and a condenser located in the lowest available part of said passageway.

In testimony that I claim the foregoing I have hereunto set my hand.

` THEGDORE BAKER. Witnesses:

C. R. MUDGE, A. M. GORMAN. 

